1. Field Of The Invention
This invention relates, in general, to conveyors and, more specifically, to roller conveyors.
2. Description Of The Prior Art
In many industries, conveyors are employed to convey articles, parts, etc., between various assembly or work stations. A typical conveyor is a so-called roller conveyor which includes a plurality of aligned rollers rotated by a drive means, such as a motor-driven chain and sprocket assembly. One or more rollers are mounted on each of a series of aligned drive shafts to propel the articles, parts, etc., along the conveyor.
Due to tolerance build-up in the manufacture of each roller, it is difficult to precisely align the rollers along the plane of the conveyor to provide a flat surface along which the articles are conveyed. Thus, the upper surface of successive rollers can vary in height such that one or more rollers can be disposed slightly above the upper surface of the adjacent rollers. Furthermore, the conveyed articles frequently have projections or variations in the surface which engage the conveyor, such as flash on a casting. Such projections or protrusions can engage the roller which is raised slightly above the proceeding rollers and stop the article or part from making further progress along the conveyor.
The undesirable build-up of tolerances in rollers is a particular problem in friction-type roller conveyors in which each roller is constructed of the plurality of components, each of which has varying size tolerances. Particularly, each roller includes an inner roller which is mounted on and rotated by a drive shaft. An outer roller is concentrically mounted about the inner roller and is frictionally driven by the inner roller. When an article is stopped on the conveyor for a work operation, the weight of the article causes the outer roller to stall or slip with respect to the rotating inner roller until the article is again released for further movement along the conveyor. Due to the tolerance on each component of the friction roller, the overall roller size may vary by an amount which can lead to frequent stoppage of articles along the conveyor as noted above.
Thus, it would be desirable to provide a conveyor roller which overcomes the problems of previously devised conveyor rollers in which the build-up of tolerances in the rollers results in an uneven article conveying surface which causes frequent and undesired stoppage of articles as the articles are being conveyed along the conveyor. It would also be desirable to provide a conveyor roller for a friction-type roller conveyor which is both inexpensive to manufacture and adaptable to many different applications.